Former Italian prime minister Silvio Berlusconi claims he is "absolutely innocent" after being found guilty of paying for sex with an underage prostitute.

The 76-year-old was sentenced to seven years in prison and banned from holding public office by a panel of three judges in Milan.

He previously denied having sex with Karima El Mahroug, also known as Ruby the Heart Stealer, after what prosecutors claimed were erotic "bunga bunga" parties at his lavish villa in 2010.

"I was truly convinced I would be absolved because there was absolutely no possibility of being found guilty based on the evidence," he said.

"I intend to resist the persecution because I am absolutely innocent and I don't want to abandon my fight to make Italy a truly free and just country."

During his trial, the court heard dozens of young women, including Miss El Mahroug, who was 17 at the time, were paid with cash and cars to attend Berlusconi's parties and dance semi-naked for him.

Miss El Mahroug denied having sex with Berlusconi when she was 17 years old

Berlusconi was also found guilty of abuse of office by arranging to have Miss El Mahroug, now 19, released from police custody when she was arrested on suspicion of theft.

His defence claimed he believed the dancer was the niece of former Egyptian president Hosni Mubarak and wanted to avoid a diplomatic incident.

His lawyer, Niccolo Ghedini, confirmed an appeal would be lodged, describing the sentence as "beyond reality" and "completely illogical".

"The judges even went beyond the prosecutors' request (for a six-year sentence)," he added.

Berlusconi has always insisted he is being persecuted by judges as part of a political plot.

Even before judge Giulia Turri and her two female assistants returned their guilty verdicts, he told friends his guilt was a "done deal", insisting he had no chance of a fair trial because of the political bias.

Berlusconi, who was not in court for the verdict, has two levels of appeal and cannot be jailed until that process has been exhausted. Under the Italian justice system, that could take several years.

However, the verdict is likely to put further pressure on current Italian Prime Minister Enrico Letta, whose fragile coalition government is supported by Berlusconi's People Of Freedom party.

Professor Christopher Duggan, an expert on Italian history and politics at the University of Reading, said the outlook for Mr Letta's government "must now be bleak".

He said: "Berlusconi has claimed credit both for Giorgio Napolitano being re-elected as President and for burying the hatchet with the left, giving Italy a workable coalition.

"Undoubtedly, though, he and his millions of followers have been hoping there will be something of a quid pro quo for this: namely that the political persecution, as they see it, of Berlusconi by the judiciary will stop.